HF/VHF wideband power power amplifier design

Hi, i have a requirement of a power amplifier with an output power of 15W within a band of 10MHz to 100MHz, gain required around 30dBmin, thinking of using HELA-10D or mrf557 as a driver and mrf137 as final power amplifier.

i have done similar amplifiers for narrow band designs earlier,but dont have much understanding of wideband match and flat gain/ equalization for wideband amplifiers.please advice if anybody have designed similar amplifiers. (appreciate if you could suggest something considering the devices mentioned)

Regard's
jws

There are nice wideband PA reference designs at Polyfet Home Page based on transmission line transformers.

Thanks for your support,i have gone through some of the application notes,not able to see any theoretical explanations on the design part, i don't have any practical experience on constructing transmission lines using rigid coax cables and ferrite cores.what is the velocity factor considered while using coax as tx line.. any online source (similar to mouser or digikey) to buy their devices/modules?

Thanking you in anticipation
Regard's
jws

jws,

Commencing on page 10 of this document:

http://www.freescale.com/files/rf_if...note/AN721.pdf

addressed wideband transformer matching and also "Roll-off Compensation".

The app note referenced above was initially years back issued by Motorola Semiconductor, and was a reference used by many RF designers of HF and VHF amplifiers.


Designing Wide-band Transformers for HF and VHF Power Amplifiers:

http://kambing.ui.ac.id/onnopurbo/or...n/qx3Trask.pdf

The above paper covers RF transformer design and various construction techniques.


I submit the above papers hoping they can give you some inspiration and ideas on how to implement your design.

Jim

Just a few mouse clicks away, see the articles tab at the polyfet homepage.

Of course, TL transformers are not restricted to semi rigid. It's advantageous however, because you achieve low loss with small dimensions and there's also a large range of characteristic impedances available. Semi rigid follows simple transmission line equations, you find the data in manufacturer catalogs as well Semi-Rigid Coaxial Cable - Micro-Coax

Thanks a lot,these notes are quite useful,currently i am trying to construct one transformer on my own and test it,may need some help later on how to verify the design parameters.

jws,

I came across one more app note dealing with wideband transformer-style matching, although the power level is about 13 dB over your goal, it may nonetheless contain a useful idea or two:

http://www.communication-concepts.co...13300Sharp.pdf


And, if you get a chance, pls click the 'helped' button if this material was at all helpful.

Regards,

Jim

PS. I actually have one of these amplifiers described in the app note in hand, although I have not had a chance to bench test it yet.